WirelessHART® is a highly reliable, easy to deploy wireless communications protocol for process automation applications. It adds wireless capabilities to HART technology while maintaining compatibility with existing HART devices, commands, and tools. WirelessHART® uses mesh networking technology. Each device in a mesh network can serve as a router for messages from other devices. In other words, a device doesn’t have to communicate directly to a gateway, but just forward its message to the next closest device. This extends the range of the network and provides redundant communication routes to increase reliability, particularly in the difficult radio environment found in process facilities.
There are four fundamental, recommended network design rules.
“Rule of Five Minimum”
Every WirelessHART network should have a minimum of five WirelessHART devices within effective range of the Gateway.
“Rule of Three”
Every WirelessHART device should have a minimum of three neighbors with in effective range.
“Rule of Percentages”
Every WirelessHART network with greater than five devices should have a minimum of 25 percent of devices within effective range of the Gateway to ensure proper bandwidth and eliminate pinch points.
“Rule of Maximum Distance”
Wireless devices with update rates faster than two seconds should be within two times the effective range of wireless devices from the Gateway.